Crossing a busy residential road at mid-block in this densely populated Washington suburb can be a challenge  even after rush hour. But the notorious stretch of road confronting Widmer on this sunny morning used to be worse.

Alexandria recently installed four flat-topped speed humps  known as "speed tables"  along a quarter-mile stretch, flanked by a park and a supermarket. Those humps reduced average speeds by nearly 25 miles an hour and cut traffic by up to 7 percent.

"They definitely have helped slow traffic," Widmer says. But in her next breath, she admits having some conflicting feelings: "As a pedestrian, I appreciate them. As a driver, I hate them."

Many drivers have a similar sense of ambiguity about traffic-calming measures as more cities try to change bad driving behavior and make neighborhood streets more pedestrian-friendly.

Cities are also installing textured crosswalks, traffic circles, and sidewalk "bulb-outs" that remove the shoulder and extend walkways up to the road. Speed humps and tables, however, are the most common devices used, according to a study by the Institute of Transportation Engineers.

Such measures have been a fixture on many European roads since the late 1960s, according to the ITE. In the US, though, such devices didn't catch on beyond such cities as Berkeley, Calif., and Eugene, Ore.

"Traffic calming is still a new phenomenon in our country," says Dan Burden, executive director of Walkable Communities Inc., a Florida-based nonprofit that advises neighborhoods how to become more pedestrian-friendly.

Today, more communities are finally addressing citizens' complaints about traffic, he says. But the solutions usually are "site specific" and often result in an abundance of "unwarranted stop signs." This approach creates new problems, Mr. Burden says, like "jack-rabbit driving," in which drivers quickly accelerate and break hard between signs.

Most municipalities, in fact, stumble through a series of stages before they reach a level of understanding about how to effectively address traffic problems, Burden notes.

Early enthusiasm

For example, in the mid-1990s, Montgomery County, Md., moved rapidly to install speed humps throughout the suburban county. This led to a backlash that included an "antihump" petition and a lawsuit. In 1998, the county placed a moratorium on new speed humps. While it has since lifted the ban, the county significantly tightened its traffic-calming eligibility rules.

Robert Wells, senior engineer and technician of Montgomery County's traffic-calming program, says the community today generally favors the humps. But sometimes he fields calls from residents who initially supported the measures and now have a case of buyers' remorse.

"They didn't realize that that many were going to go in," Mr. Wells says, describing a one-mile stretch of residential road that boasts 20 speed humps.

In Alexandria, city planners have installed the humps only in neighborhoods where 65 percent of affected homeowners ask for them, says Paul DeMaio, Alexandria's new traffic-calming coordinator.

After receiving a neighborhood traffic-calming request, the city conducts a detailed study of the site to determine if it meets the criteria for speed and excessive volume. To qualify, more than 15 percent of drivers must travel at least 5 m.p.h. over the posted limit, or more than 300 vehicles an hour must pass along that section of residential road.

Bill Hendrickson, president of the Del Ray citizens' association in Alexandria, says there is "strong support for traffic calming overall" among residents of his leafy neighborhood.

The aim is not to impede traffic, he says. But Mr. Hendrickson says he hopes the speed humps will discourage drivers from cutting through the neighborhood as they try to avoid the nearby commuter artery. "They don't have the right to drive as fast as they like," Hendrickson says.

The downside of humps

Opponents, however, say the humps are annoying at best and can actually do more harm than good. Alexandria resident Mr. Duncan, who declined to give his first name, says indignantly: "First they're telling me to wear a seat belt, then you can't use a cellphone in the car. Now, you're going to tell me how to drive my car on the roads?"

Rick Hall, who heads Americans Against Traffic Calming out of Austin, Texas, says the humps can cause back and head injuries to riders who bounce up and hit the ceiling of their car. They also slow down emergency vehicles.

Alexandria Fire Chief Thomas Hawkins says the speed tables have created additional wear and tear on the city's emergency vehicles. In fact, he says the fire department is working with the city to consider an alternative to speed tables: "speed cushions," which provide grooves wide enough for fire trucks to pass through unimpeded.

The city is also establishing emergency routes that will remain free of speed tables, says Mr. DeMaio, the Alexandria coordinator.

Despite the controversy, the traffic-calming movement in the US will likely accelerate over the next decade, experts say. Amanda Wallingford, who walks her dog in Alexandria, is resigned to the proliferation of humps. "They can be annoying, but they're a necessary evil," she says.